Add: Validation for correctly enabled material extensions

Also adds some optional tests I've had lying around locally for a while

CMakeLists.txt

@@ -43,7 +43,7 @@ else()
     find_package(simdjson CONFIG)
     if (simdjson_FOUND)
         message(STATUS "fastgltf: Found simdjson config")
-        target_link_libraries(fastgltf PRIVATE simdjson::simdjson)
+        target_link_libraries(fastgltf PUBLIC simdjson::simdjson)
     else()
         # Download and configure simdjson
         set(SIMDJSON_TARGET_VERSION "3.6.3")

src/fastgltf.cpp

@@ -882,6 +882,34 @@ fg::Error fg::validate(const fastgltf::Asset& asset) {
 		if (material.pbrData.metallicRoughnessTexture.has_value() &&
 		    isInvalidTexture(material.pbrData.metallicRoughnessTexture->textureIndex))
 			return Error::InvalidGltf;
+
+		// Validate that for every additional material field from an extension the correct extension is marked as used by the asset.
+		if (material.anisotropy && !isExtensionUsed(extensions::KHR_materials_anisotropy))
+			return Error::InvalidGltf;
+		if (material.clearcoat && !isExtensionUsed(extensions::KHR_materials_clearcoat))
+			return Error::InvalidGltf;
+		if (material.iridescence && !isExtensionUsed(extensions::KHR_materials_iridescence))
+			return Error::InvalidGltf;
+		if (material.sheen && !isExtensionUsed(extensions::KHR_materials_sheen))
+			return Error::InvalidGltf;
+		if (material.specular && !isExtensionUsed(extensions::KHR_materials_specular))
+			return Error::InvalidGltf;
+#if FASTGLTF_ENABLE_DEPRECATED_EXT
+		if (material.specularGlossiness && !isExtensionUsed(extensions::KHR_materials_pbrSpecularGlossiness))
+			return Error::InvalidGltf;
+#endif
+		if (material.transmission && !isExtensionUsed(extensions::KHR_materials_transmission))
+			return Error::InvalidGltf;
+		if (material.volume && !isExtensionUsed(extensions::KHR_materials_volume))
+			return Error::InvalidGltf;
+		if (material.emissiveStrength != 1.0f && !isExtensionUsed(extensions::KHR_materials_emissive_strength))
+			return Error::InvalidGltf;
+		if (material.ior != 1.5f && !isExtensionUsed(extensions::KHR_materials_ior))
+			return Error::InvalidGltf;
+		if (material.packedNormalMetallicRoughnessTexture && !isExtensionUsed(extensions::MSFT_packing_normalRoughnessMetallic))
+			return Error::InvalidGltf;
+		if (material.packedOcclusionRoughnessMetallicTextures && !isExtensionUsed(extensions::MSFT_packing_occlusionRoughnessMetallic))
+			return Error::InvalidGltf;
 	}
 
 	for (const auto& mesh : asset.meshes) {

tests/optional_tests.cpp

@@ -0,0 +1,18 @@
+#include <catch2/catch_test_macros.hpp>
+
+#include <fastgltf/types.hpp>
+
+TEST_CASE("Test basic Optional interface", "[optional-tests]") {
+	// We have no specialization for std::uint32_t, and therefore this is just
+	// a std::optional with a bool field padded by 3 bytes.
+	fastgltf::Optional<std::uint32_t> optional;
+	static_assert(sizeof(optional) > sizeof(std::uint32_t));
+}
+
+TEST_CASE("Test Optional float specialization", "[optional-tests]") {
+	fastgltf::Optional<double> doptional;
+	static_assert((std::numeric_limits<double>::is_iec559 && sizeof(doptional) == sizeof(double)) || !std::numeric_limits<double>::is_iec559);
+
+	fastgltf::Optional<float> foptional;
+	static_assert((std::numeric_limits<float>::is_iec559 && sizeof(foptional) == sizeof(float)) || !std::numeric_limits<float>::is_iec559);
+}